Papers by Stavros Vologiannidis
A new approach on the linearization of 2-D polynomial matrices
2019 6th International Conference on Control, Decision and Information Technologies (CoDIT)
In this paper we propose a generic approach to reduce a $2-L$ square polynomial matrix of arbitra... more In this paper we propose a generic approach to reduce a $2-L$ square polynomial matrix of arbitrary degree(s), to first-order matrix pencils of the form $sE_{1}+zE_{2}+A$, utilizing the framework of zero coprime equivalence (ZC-E). This generic approach is in turn employed to derive a series of ZC-E matrix pencils, which can be obtained “by inspection” of the coefficients of the original bivariate polynomial matrix. Improving similar constructions of first order pencils in the literature, our approach results in matrix pencils whose size increases linearly with the degrees of the indeterminates of the original polynomial matrix.
On the reduction of repetitive processes into singular and non-singular Roesser models
Multidimensional Systems and Signal Processing, 2021
In this paper we present new methods for the reduction of a polynomial system matrix describing a... more In this paper we present new methods for the reduction of a polynomial system matrix describing a discrete linear repetitive process, to equivalent singular and non-singular 2-D state space representations. Particularly, a zero coprime system equivalence transformation resulting in a singular Roesser state space model, preserving the core algebraic structure of the original system matrix, is proposed. As a second step utilizing the singular Roesser model introduced, we further reduce the system to a non-singular, zero coprime system equivalent Roesser model. Both models are constructed by inspection or by applying elementary matrix manipulations and have significantly smaller dimensions compared to similar reductions found in the literature.
Multidimensional Systems and Signal Processing, 2019
In this paper we propose a novel approach for the reduction of a 2-D rectangular polynomial matri... more In this paper we propose a novel approach for the reduction of a 2-D rectangular polynomial matrix of arbitrary degree, to first-order matrix pencils of the form s E 1 +z E 2 + A, utilizing the framework of zero coprime equivalence (ZC-E). The proposed approach is in turn employed to derive a series of ZC-E matrix pencils, which can be obtained "by inspection" of the coefficients of the original bivariate polynomial matrix. Improving similar constructions of first order pencils available in the literature, our approach results in matrix pencils whose size increases linearly with the degrees of the indeterminates of the original polynomial matrix. From a system-theoretic point of view, the proposed method, provides the algebraic tools to transform a high order bivariate linear system, into a zero coprime system equivalent first order representation. Notably, one of the proposed transformation techniques gives rise to generalized 2−D Roesser models.
Electronic Journal of Linear Algebra, 2016
In the present note, a new characterization of strong linearizations, corresponding to a given re... more In the present note, a new characterization of strong linearizations, corresponding to a given regular polynomial matrix, is presented. A linearization of a regular polynomial matrix is a matrix pencil which captures the finite spectral structure of the original matrix, while a strong linearization is one incorporating its structure at infinity along with the finite one. In this respect, linearizations serve as a tool for the study of spectral problems where polynomial matrices are involved. In view of their applications, many linearization techniques have been developed by several authors in the recent years. In this note, a unifying approach is proposed for the construction of strong linearizations aiming to serve as a bridge between approaches already known in the literature.
Computation of the general solution of a multivariate polynomial matrix Diophantine equation
21st Mediterranean Conference on Control and Automation, 2013
ABSTRACT The algorithm presented in [21] provides a method for the computation of the general sol... more ABSTRACT The algorithm presented in [21] provides a method for the computation of the general solution of a polynomial matrix Diophantine equation. In this work we extend this algorithm for the n-D PMDE.We present a method to efficiently address the division of multivariate polynomials. The theory is implemented via illustrative examples.
The present paper is a survey on linear multivariable systems equivalences. We attempt a review o... more The present paper is a survey on linear multivariable systems equivalences. We attempt a review of the most significant types of system equivalence having as a starting point matrix transformations preserving certain types of their spectral structure. From a system theoretic point of view, the need for a variety of forms of polynomial matrix equivalences, arises from the fact that different types of spectral invariants give rise to different types of dynamics of the underlying linear system. A historical perspective of the key results and their contributors is also given.
Proceedings of the 20th IEEE International Symposium on Intelligent Control, ISIC '05 and the 13th Mediterranean Conference on Control and Automation, MED '05, 2005
In an earlier paper by the present authors, a new family of companion forms associated with a reg... more In an earlier paper by the present authors, a new family of companion forms associated with a regular polynomial matrix was presented, generalizing similar results by M. Fiedler who considered the scalar case. This family of companion forms preserves both the finite and infinite elementary divisor structure of the original polynomial matrix, thus all its members can be seen as linearizations of the corresponding polynomial matrix. In this note, its applications on polynomial matrices with symmetries, which appear in a number of engineering fields, are examined.
Mathematics of Control, Signals, and Systems, 2011
In [1] and [2] a new family of companion forms associated to a regular polynomial matrix T (s) ha... more In [1] and [2] a new family of companion forms associated to a regular polynomial matrix T (s) has been presented, using products of permutations of n elementary matrices, generalizing similar results presented in [3] where the scalar case was considered. In this paper, extending this "permuted factors" approach, we present a broader family of companion like linearizations, using products of up to n(n − 1)/2 elementary matrices, where n is the degree of the polynomial matrix. Under given conditions, the proposed linearizations can be shown to consist of block elements where the coefficients of the polynomial matrix appear intact. Additionaly we provide a criterion for those linearizations to be block symmetric. We also illustrate several new block symmetric linearizations strictly equivalent to the original polynomial matrix T (s) where in some of them, the constraint of nonsingularity of the constant term and the coefficient of maximum degree is not a prerequisite.
This report describes our joint work on implementation of effective numerical routines for two-va... more This report describes our joint work on implementation of effective numerical routines for two-variable polynomial matrices in the MATHEMATICA software. New functions are connected to the already created program package, being developed at the Czech Technical University in Prague, which calculates only with polynomial matrices in one variable. As the first step, new polynomial object for 2-D polynomial matrix was created in the MATHEMATICA programming language. This was essential for good integration with the polynomial package mentioned above. Implementation of a bunch of efficient and reliable numerical routines followed.
Lecture Notes in Computer Science, 2014
The WISE 2014 challenge was concerned with the task of multi-label classification of articles com... more The WISE 2014 challenge was concerned with the task of multi-label classification of articles coming from Greek print media. Raw data comes from the scanning of print media, article segmentation, and optical character segmentation, and therefore is quite noisy. Each article is examined by a human annotator and categorized to one or more of the topics being monitored. Topics range from specific persons, products, and companies that can be easily categorized based on keywords, to more general semantic concepts, such as environment or economy. Building multi-label classifiers for the automated annotation of articles into topics can support the work of human annotators by suggesting a list of all topics by order of relevance, or even automate the annotation process for media and/or categories that are easier to predict. This saves valuable time and allows a media monitoring company to expand the portfolio of media being monitored. This paper summarizes the approaches of the top 4 among the 121 teams that participated in the competition.
Applied Sciences
Urban environments are evolving rapidly in big cities; keeping track of these changes is becoming... more Urban environments are evolving rapidly in big cities; keeping track of these changes is becoming harder. Information regarding urban features, such as the number of trees, lights, or shops in a particular region, can be crucial for tasks, such as urban planning, commercial campaigns, or inferring various social indicators. StreetScouting is a platform that aims to automate the process of detecting, visualizing, and exporting the urban features of a particular region. Recently, the advent of deep learning has revolutionized the way many computer vision tasks are tackled. In this work, we present StreetScouting, an extensible platform for the automatic detection of particular urban features of interest. StreetScouting utilizes several state-of-the-art computer vision approaches including Cascade R-CNN and RetinaFace architectures for object detection, the ByteTrack method for object tracking, DNET architecture for depth estimation, and DeepLabv3+ architecture for semantic segmentatio...
Hate speech and personal attack dataset in Greek social media
This dataset contains 61481 Greek tweet ids and corresponding annotations for Hate Speech label a... more This dataset contains 61481 Greek tweet ids and corresponding annotations for Hate Speech label and 61481 Greek tweet ids and corresponding annotations for Personal attack label. The creation of this dataset was part of the project DACHS "A Data-driven Approach to Countering Hate Speech" funded by the Rights, Equality and Citizenship Programme of the European Union.
Hate speech and personal attack dataset in French social media
This dataset contains 29109 French tweet ids and corresponding annotations for Hate Speech label ... more This dataset contains 29109 French tweet ids and corresponding annotations for Hate Speech label and 39109 French tweet ids and corresponding annotations for Personal attack label. The creation of this dataset was part of the project DACHS "A Data-driven Approach to Countering Hate Speech" funded by the Rights, Equality and Citizenship Programme of the European Union.
Hate speech and personal attack dataset in English social media
This dataset contains 92022 English tweet ids and corresponding annotations for Hate Speech label... more This dataset contains 92022 English tweet ids and corresponding annotations for Hate Speech label and 90892 English tweet ids and corresponding annotations for Personal attack label. The creation of this dataset was part of the project DACHS "A Data-driven Approach to Countering Hate Speech" funded by the Rights, Equality and Citizenship Programme of the European Union.
Hate speech and personal attack dataset in Spanish social media
This dataset contains 37688 Spanish tweet ids and corresponding annotations for Hate Speech label... more This dataset contains 37688 Spanish tweet ids and corresponding annotations for Hate Speech label and 37688 Spanish tweet ids and corresponding annotations for Personal attack label. The creation of this dataset was part of the project DACHS "A Data-driven Approach to Countering Hate Speech" funded by the Rights, Equality and Citizenship Programme of the European Union.
Hate speech and personal attack dataset in German social media
This dataset contains 43735 German tweet ids and corresponding annotations for Hate Speech label ... more This dataset contains 43735 German tweet ids and corresponding annotations for Hate Speech label and 43734 German tweet ids and corresponding annotations for Personal attack label. The creation of this dataset was part of the project DACHS "A Data-driven Approach to Countering Hate Speech" funded by the Rights, Equality and Citizenship Programme of the European Union.
A Workflow for Designing Video Processing Pipelines with PYNQ
2021 11th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications (IDAACS), 2021
Video processing acceleration is a vital task in a number of appications, including vision-based ... more Video processing acceleration is a vital task in a number of appications, including vision-based robotics. A workflow for the design of video pipelines based on the heterogeneous chip Zynq-7020 and the PYNQ-Z1 board is proposed. A video pipeline featuring a custom IP block based on AXI4-Stream interface is presented. The structure of a processing pipeline partitioned into programmable logic and the ARM processing system is outlined. The integration of the video pipeline with ROS nodes for hardware acceleration is proposed. The presented workflow is beneficial for education and can expedite research projects.
EUROPA — A ROS-based Open Platform for Educational Robotics
2019 10th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications (IDAACS), 2019
Introducing robotics to young students is becoming very important for modern education of all lev... more Introducing robotics to young students is becoming very important for modern education of all levels. This paper presents EUROPA, an educational robot, which was developed as a handy, low-cost and extensible platform of high capabilities, suitable to bring robotics to secondary school students and beyond. It is designed as a system of easily accessible hardware and open software that can be incorporated in STEM classes of all levels in the Greek education system. The proposed robot incorporates Robot Operating System (ROS) and is based on Python which is already taught in Greek modula on informatics, similarly to other countries worldwide. We present in detail the hardware and software architecture of our robot and define its advantages among similar state-of-the-art educational robots. EUROPA platform was introduced to a class of secondary school students with robotic experience in Lego Mindstorms, and was assessed with very positive results.
IEEE/WIC/ACM International Conference on Web Intelligence, 2019
This paper proposes a machine learning approach to part-of-speech tagging and named entity recogn... more This paper proposes a machine learning approach to part-of-speech tagging and named entity recognition for Greek, focusing on the extraction of morphological features and classification of tokens into a small set of classes for named entities. The architecture model that was used is introduced. The greek version of the spaCy platform was added into the source code, a feature that did not exist before our contribution, and was used for building the models. Additionally, a part of speech tagger was trained that can detect the morphology of the tokens and performs higher than the state-of-the-art results when classifying only the part of speech. For named entity recognition using spaCy, a model that extends the standard ENAMEX type (organization, location, person) was built. Certain experiments that were conducted indicate the need for flexibility in out-of-vocabulary words and there is an effort for resolving this issue. Finally, the evaluation results are discussed.
Sensors, 2020
Robots have become a popular educational tool in secondary education, introducing scientific, tec... more Robots have become a popular educational tool in secondary education, introducing scientific, technological, engineering and mathematical concepts to students all around the globe. In this paper EUROPA, an extensible, open software and open hardware robotic platform is presented focusing on teaching physics, sensors, data acquisition and robotics. EUROPA’s software infrastructure is based οn Robot Operating System (ROS). It includes easy to use interfaces for robot control and interaction with users and thus can easily be incorporated in Science, Technology, Engineering and Mathematics (STEM) and robotics classes. EUROPA was designed taking into account current trends in educational robotics. An overview of widespread robotic platforms is presented, documenting several critical parameters of interest such as their architecture, sensors, actuators and controllers, their approximate cost, etc. Finally, an introductory STEM curriculum developed for EUROPA and applied in a class of high...
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Papers by Stavros Vologiannidis